In traditional photography, including cinematography, many different processes take place during the preparation of a displayed image, including motion pictures. The imaging chain comprises the basic steps of image capture, image processing, and image display. In photographic film based systems, after capture of a scene on photographic origination film, the image processing step of the imaging chain may include multiple development steps, contact printing between films of different generations, and optical printing from film to film, before projection of a final print image. Each step in the image chain can influence the content of an image and therefore the appearance of the image. These influences can be broken down in a variety of ways. Many of these influences give the final image a specific appearance or “look”. This appearance or “look” adds either artistic value to the final image or makes the image more pleasing to the viewer. While photographic systems are generally designed to maximize realistic reproduction of an original scene, the selection of film stock and processing conditions can change the “look” of the resulting image, and cinematographers make such selections to obtain specific desired looks.
By way of confirming this point, under a section entitled “THE FIELD OF ART”, the Encyclopedia Britannica states one “view of art is based on the assumption that art is what survives a series of ‘tests’ given to objects that function as art. When such an object is initially presented to the view of people other than its creator, it could be viewed as representing a ‘claim to art.’ When it is accepted by large numbers of people in a society or by its established elites or by other artists and art critics, it could be said to have become a popularly, or authoritatively, or professionally validated work of art. But the ultimate test of its artistic quality is whether it can transcend the boundaries of time and space and be accepted by other peoples in other areas.” Film looks in motion picture of themselves or as components of the overall creative process can be said to meet such “tests”.
One such “look” is the photo-realistic or film “look” where by virtue of the processes of creating the final experience in the theater influences are added which to viewers make the image more pleasing than if these influences were not present. The term “photo-realistic” is generally understood by professional cinematographers or photographers to include the characteristics of the photographic film that captured the scene. They understand that in a darkened theatrical viewing environment the eye is more sensitive to the presence or absence of specific characteristics than when viewing a reflection print in ambient light. They also understand that viewers can be aware of the presence of image differences, although they may be able to point to or specifically identify the difference. Often the presence or absence of these differences can affect the impression of quality or satisfaction the viewer has of the overall theatrical experience. Specifically for example, the steps of capturing on film, developing the film, step printing or contact printing the film (often repeated times) and then projecting the film introduces added influences. When an image is generated using an image chain that lacks film steps or has a reduced number of film steps, the appearance of these photo realistic or film influences in the final image may be lacking or substantially diminished.
Electronic video cameras have been available for some time for capturing original scene information in electronic form. While image data in electronic form is generally easier to edit and modify than an image on photographic film, images recorded electronically have generally been regarded as of poorer quality than images recorded on photographic film when displayed. Also, the proliferation of various video formats has resulted in a variety of different resulting looks for electronically captured images.
In recent years, hybrid photographic film/electronic processing imaging systems have become prevalent. Hybrid systems typically comprise capturing original scene information on photographic film, scanning the film image to provide digital image data to allow for digital image data processing, and subsequently rewriting the processed digital image data to photographic film for display, or directly displaying the processed digital data by electronic means. Insertion of an intermediate electronic image data processing step allows, e.g., for the creation of digital special effects, or changing the “look” of the resulting displayed image, while retaining the benefits of capturing the original scene on film.
With the rapid advance of semiconductor electronics, it is now possible to contemplate the time when high quality motion pictures will be captured in the real world and on movie sets using electronic cameras such as CCD cameras. These cameras would likely use multiple CCDs, each operating with more than one to and up to six million pixels. One danger of electronic cameras is that although from a digital point of view they may generate image data that minimizes the artifacts normally associated with electronic capture, the images that result from this data are not seen as photo-realistic. Further, modern CCD based motion cameras often have literally thousands of combinations of possible camera instrumentation settings that are available to the cinematographer. Many of these settings have significant impact on the look of the captured image, and therefore selection of certain combinations may have unintended results with respect to the image look actually obtained relative to a desired look. This can represent a real threat to the cinematographer as he generally has only one opportunity to capture a scene and if the image data does not have the look the director desires it may not be possible to repeat the shoot.
Some attempts have been made to electronically introduce specific film like effects in electronically captured images. Examples include U.S. Pat. No. 4,935,816, which describes specific and limited digital processing techniques for achieving a film “look” in NTSC quality video. Examples of other prior art include attempting to introduce the appearance of film grain into images is found for example in electronic image editing packages such as Adobe PhotoShop and Adobe Premier. U.S. Pat. No. 5,641,596 discloses superior technology for adjusting film grain properties in digital images that provides a greater degree of photo-realism, and addresses adding grain to film images after digital processing of the film image data has removed the grain. U.S. Pat. No. 5,457,491 is directed towards a system for producing an image on a first medium, such as video, simulating the appearance of an image on a second medium, such as motion picture or other photographic film. Other patents such as U.S. Pat. Nos. 5,512,956, 5,502,489 and 5,442,407 show techniques for filtering and processing electronic images. Some of these methods are based on certain parameters within the image. However no attempt is made to characterize elements upstream in the imaging chain or the underlying imaging parameters required to produce a specific “look”. U.S. Pat. No. 5,696,850 does attempt to characterize the upstream and downstream elements to achieve an “optimum sharpening level” however this level is not related to artistic intent or “look” characteristics. Nor is there any regard between sharpening and other essential image characteristics such as grain and noise. The invention does not specify “look” specifications or “look” specification points within the system. Furthermore, it does not specify the concept of reference looks and setting an intended look either with respect to the scene or with respect to a reference “look”.
The fact that digital image data may be easily modified may result in the final displayed image being something other than the “look” which the cinematographer originally intended. Cinematographers involvement is often primarily before and during the photographic shoot. Electronic processing using either film based or electronic based cameras occurs necessarily after the photographic shoot. Supervising this electronic process to ensure that the intended “look” is maintained can require a considerable amount of additional time on the part of the Cinematographer.
With the recent advancements in electronic image capture and electronic image data processing, it would be desirable to provide a system whereby a source digital image data signal may be modified in an imaging chain to obtain digital image data which will provide a specific desired “look” without restrictions as to the origin of the source digital image data. Especially with electronically captured digital images, it may be necessary to first analyze or sense the characteristics of the camera images captured at the specific combination of camera settings employed in order to subsequently obtain a desired reference look or to define a new look in terms of the images produced by digital cameras. By providing a cinematographer with a way to specify a specific “look” and then applying metrics to assess how that “look” is achieved, the cinematographer may be freed from extensive involvement during the electronic processing stage.